1. Field
One or more exemplary embodiments relate to a lead-free solder, a solder paste, and a semiconductor device.
2. Description of the Related Art
Printed circuit boards (PCBs) have been widely used in home appliances, such as televisions, mobile phones, or computers. Recently, a lot of PCBs have been used in automobiles. For solders that are used in home appliances, a lot of Sn—Pb alloy group products have been used. In particular, lead (Pb) acts as a component that determines wettability, strength, and mechanical characteristics of a Sn—Pb alloy. Also, since lead is included in the Sn—Pb alloy, the melting point of the solder may be lowered to 183° C., and thus, thermal damage that occurs in a soldering process between an electronic part and a semiconductor device can be prevented.
Due to the strict environmental regulations in relation to Pb, a lead-free solder alloy, that is, a ternary system of Sn—Ag—Cu has been proposed. However, since the ternary system is weak to oxidation and has low spreadability and low wettability, workability is poor and resistance to impact is low. Also, the ternary system is inappropriate for an atmosphere of high temperature of over 130° C. as in an engine room of an automobile, and is expensive since Ag is included.